Project Summary Adolescence represents a critical period of heightened risk-taking, giving rise to dangerous health-related risk behaviors such as substance use. The quality of the parent-adolescent relationship is one robust predictor of adolescent substance use and health-compromising risk behavior. Critically however, the family environment, including the parent-adolescent relationship, may not affect youth outcomes uniformly. Individual differences in neurobiological susceptibility to the social environment may moderate the influence of the parent-adolescent relationship on youth behavior, such that adolescents who are highly tuned to the social environment may fare the worst in harsh, unsupportive family contexts and may be most at risk for substance use. Thus, greater understanding of susceptibility factors is key for targeting at-risk youth and informing future substance use prevention. The proposed NRSA will represent the first study to examine adolescent social reward sensitivity, a key neurobiological marker of adolescent's susceptibility to social inputs, as a moderator of the parent-adolescent relationship's influence on adolescent risk-taking and substance use. Specifically, the proposed NSRA will employ a two-prong multimethod approach supported by the applicant's sponsor. First, data will be analyzed from a well-characterized longitudinal dataset of 148 adolescents, followed for three years beginning at ages 12-13. Adolescents completed fMRI social reward paradigms at baseline and reported on family relationships, substance use, and other risk behaviors at each yearly time point. Second, 75 adolescents (ages 15-16) will be recruited from this sample to complete a novel 4-week ecological momentary assessment (EMA) of daily parent-adolescent interactions and risk behavior (e.g., rule breaking, substance use) which will be completed during wave 4 of the R01 parent study. This complementary approach will allow us to examine social reward sensitivity as a neurobiological susceptibility marker across macro and micro timescales. Consistent with NIDA's strategic objectives, this project will advance basic scientific understanding of neurobiological and social factors conferring vulnerability for substance use initiation (NIDA 2016-2020, Obj 1.1) Further, this fellowship will provide the crucial training needed to establish this applicant's independent research program in adolescent substance use prevention through training in social-affective neuroscience, data-driven network analyses, intensive time-series method, adolescent substance use, and research dissemination.